There are sprinkler systems of various main types available for protection against fire. In a first type, a central detector releases a main valve which in turn distributes fire extinguishing fluid, generally water, to a number of sprinkler outlets. As the water in the rest position is not all the way up to the outlets, it can take quite a few seconds for the water to reach the place where the fire has started after the detector has activated the system.
This type of sprinkler is therefore unsuitable in premises where a fire can be expected to spread very rapidly. The advantages of a system of this type are that all of the heads are activated at one and the same time, and that it is relatively cheaper than other systems, as only one valve and one detector are required.
In another main type, the water, or the fire extinguishing fluid used, is already all the way up to the sprinkler heads in the waiting position, and the sprinkler heads can then be equipped with blocking means of their own, which are also activated individually. A system of this type will be very rapid, but requires a more complete activation system or a separate activator for each sprinkler head.
The releasing system hitherto most commonly used for separate sprinkler heads is based upon the use of special glass bulbs which contain a highly temperature sensitive fluid which at a predetermined temperature above the normal temperature causes the bulb to burst. By utilizing such a bulb as a blocking component in a sealing system arranged at the respective sprinkler head, a temperature sensitive individual releasing system with a high degree of functioning reliability is obtained. If the temperature exceeds the predetermined value, the bulb is thus crushed from the inside, and the blocking of the outlet of the sprinkler head is removed and the fire extinguishing fluid instantaneously begins to flow out. The drawback of this system in its more general form is that each sprinkler head must be activated individually. It can also be a drawback that most often only the sprinkler head or heads nearest the place where the fire starts are activated, and that this takes place only when the fire has developed sufficiently to produce a marked rise in temperature.
There is now a possibility of achieving simultaneous releasing of all the sprinkler heads comprised in the circuit if, for instance, these are provided with remote-controllable activators connected with an UV sensitive or other type of detector which reacts in case of a fire. The most prominent advantage of a UV sensitive detector would be that it can be made to react instantaneously to the first naked flame that appears, although the detector is not therefore released by e.g. bright sunlight. Thus, the UV detector need not, as in the case of temperature or smoke sensitive detectors, wait until a predetermined limit value is exceeded. The UV detector is thus released at a considerably earlier stage of a fire than detectors of other types. Regardless of the actual advantages of the UV detector it is, of course, quite possible to arrange for simultaneous releasing of a plurality of sprinkler heads in accordance with what is described in the following without the aid of UV detectors but by means of a pressure, smoke, or heat sensitive detector. The most simple way of simultaneously releasing a number of sprinkler heads of the type where the water is all the way up to the heads which are located at a distance from each other is to provide each and every head with a pyrotechnical activator which when it is activated by an ignition function connected together with a detector, blows away the blocking system that blocks the outlet of the sprinkler head.
In the Swedish patent application No. 7713209-0, which corresponds to U.S. Pat. No. 4,281,718 issued to Claussen and Broberg and commonly assigned, an unusually practical activator is described which is intended to be used in the way described above. Its function is based upon a very small pyrotechnical charge which, when it is ignited electrically, throws a charge of powder consisting of e.g. a fine-grained metal powder against a bulb of the type described above, which is crushed at the same time as the charge of powder is broken up into separate grains of powder. The bulb, which thus has a blocking function at the seal at the outlet of the sprinkler head, being crushed, the seal at the outlet falls away, and the fire extinguishing fluid begins to flow out.
Such electrically ignited pyrotechnical activators can be connected to the ignition function, e.g. ignition generators or battery igniters, which are activated by an appropriate detector of the type indicated above.
The activator described briefly above, combined with a UV detector, thus gives a rapid and very reliable function when it is a question of naked fire. As the temperature sensitive bulb is comprised in the system, also temperature dependent releasing is obtained, but then only of the sprinkler heads which are subjected to the elevated temperature.